The present invention relates to pressure sensing apparatus and, more particularly, to novel structures of pressure sensing probes communicating with a manifold.
In systems for measuring fluid flow through an enclosed duct or conduit it is sometimes necessary or desirable to sense the pressure of the fluid at a plurality of locations and to communicate the pressure from each location to a common manifold. Both the pressure sensing means and the manifold are commonly in the form of a hollow tube, the manifold of course being of significantly larger diameter.
An example of the general type of prior art apparatus wherein the present invention may be advantageously employed is found in U.S. Pat. No. 3,685,355, wherein pressure measuring apparatus is permanently installed in a duct through which air flows in one direction. Total pressure is sensed at a number of locations in a transverse plane of the duct by impact tubes having open ends towards which the air flow is directed. From the open end each tube extends in the direction of air flow and is then bent at approximately 90.degree. and inserted in a drilled opening in the manifold tube. The impact tube is of the same inside diameter from the open end to the end communicating with the manifold.
In other prior art devices, the impact tubes may extend straight from the manifold, in the upstream direction of fluid flow, without being bent. The arrangement of sensing tubes in the aforementioned patent offers the advantage of allowing more sensor tip locations for a single manifold. However, a drilled opening in the manifold and separate connecting operation is required for each impact tube, i.e., for each sensing location.